Deterioration level of a battery (lead storage battery) is known to be determined by measuring the internal resistance of a battery (ohmic resistance component, activation polarization component, and concentration polarization).
For example, Japanese Laid-Open Patent Application No. 2001-228226 (Patent Document 1) discloses, as deterioration level determination means that measures the internal resistance of a battery, a process that is based on the fact that internal resistance varies depending on temperature as well as the charged state in which the open circuit voltage is measured; the charged state is calculated based on data from the open circuit voltage; the internal resistance of the battery during nonuse and the internal resistance when the battery has deteriorated and can no longer be used is calculated based on the charged state-resistance characteristics data; the internal resistance of the two is furthermore temperature corrected; the internal resistance is calculated based on the correlative relationship between the electric current and voltage when a target battery is discharging, and the deterioration level of the battery is calculated from the internal resistances thus calculated.
Calculation means that uses actual measurements of the internal resistance determines the internal resistance at the time of measurement based on data sampled in advance on the basis of change in the discharge current and reduced voltage of the battery. However, there is a problem in terms of cost to record a large amount of data and to perform all of the prescribed comparative conversion processing using onboard equipment.
In view of the above, Japanese Laid-Open Patent Application No. 2002-221559 (Patent Document 2) discloses a management device that determines the deterioration level of a battery in order to eliminate the inconvenience of making a special trip to a service station or automobile maintenance facility to determine the deterioration level of a battery.
Japanese Laid-Open Patent Application No. 2002-221559 (Patent Document 2) discloses means that has a battery, a computer that computes the battery characteristics from the terminal voltage and the discharge current of the battery, a determination unit that determines the battery deterioration level state on the basis of the battery characteristics and the battery fluid temperature, and a cranking determination unit that determines that the internal combustion engine starter apparatus is cranking, wherein the battery deterioration level state is determined during cranking.
[Patent Document 1] Japanese Laid-Open Patent Application No. 2001-228226
[Patent Document 2] Japanese Laid-Open Patent Application No. 2001-228226